1. Field of the Invention
The present invention relates to an electroluminescent element.
2. Description of the Related Art
Having a thickness of smaller than 1 mm, an electroluminescent element has many applications as a thin, power-saving light emitter. With the recent boom in mobiles, such as typically portable telephones being much popularized, an electroluminescent element is indispensable to the backlight in many portable electronic appliances. When an electroluminescent element is used for the backlight in such portable electronic appliances, its shape is naturally determined depending on the shape of the display part of the electronic appliances.
For example, when an electroluminescent element is employed for the backlight in portable telephones, it shall be composed of two light-emitting parts A and B that individually lighten the body part provided with key switches and the liquid-crystal display part for displaying telephone numbers and other informations in its window. In the electroluminescent element with that constitution, the transparent electrode film layer, the insulating layer and the back electrode layer are integrated for the two light-emitting parts.
In one example, a transparent electrode layer 42 of ITO is formed on the back surface of a transparent electrode filmlayer 41, and light-emitting layers 43, 43, which are for the region of the switch key part and for the region of the display part, respectively, are formed on the back surface of the transparent electrode layer 42, as in FIG. 4. In this, however, no light-emitting layer is provided in the throat part C, and an insulating layer 44 is provided over the both light-emitting parts A and B so as to separate them from each other. On the back surface of the insulating layer 44, formed is a back electrode layer 46, and the two light-emitting parts 43, 43 are electrically connected by the back electrode layer 46 and the transparent electrode layer 42. On the back surface of the back electrode layer 46, formed is a protective layer 47 of polyester or the like.
As having a small area, the throat part C may receive stress concentration when bent, whereby the layer of ITO, the insulating layer and the back electrode layer that are made of brittle materials are often cracked. The cracks cause electric interconnection failure in the electrode layers and insulation failure in the insulating layer, whereby the device is short-circuited.
The invention is to solve the problems noted above, and provides an electroluminescent element having at least two light-emitting parts, in which the transparent electrode leading part and the back electrode leading part that are to electrically connect the transparent electrode and the back electrode for the light-emitting parts are made of resin binder-containing conductive ink layers of materials that hardly crack against bending force.
In the electroluminescent element of the invention, the transparent electrode leading part is formed on the transparent electrode, and a flexible, insulating resin layer is formed between the back electrode leading part and the transparent electrode above which the back electrode leading part is formed, whereby the deformation resistance of the electroluminescent element is enlarged and the cracking and the electric short-circuiting to be caused by bending force could be prevented.